Spinal fixation systems used to correct spinal deformities generally consist of a series of bone fasteners anchored to the pedicles, lamina or transverse process of the vertebrae. The bone fasteners are interconnected to one another by one or more elongated spinal rods or plates. In order to access the spinal area for implantation of these spinal fixation systems and their individual components, open approach surgical techniques have historically been employed. These open procedures generally involve large skin incisions and extensive tissue retraction and resection, all which may result in considerable post-operative pain and prolonged hospital stays.
More recently, surgeons have used minimally invasive techniques to reduce the post-operative effects of spinal fixation procedures. A paraspinal approach is one form of minimally invasive technique and involves muscle splitting or muscle sparing in order to gain access to the posterior elements of the spine. Such a technique minimizes trauma to tissues adjacent the spine. Unlike open approaches where muscles and other soft tissue are cut, split, stripped and dissected, the paraspinal approach involves separation or splitting of the muscles along their fibers.
To perform a paraspinal surgical procedure, a midline skin incision is made and followed by bi/unilateral fascia incisions. The muscles are then separated to allow bilateral access to the spine via a single skin incision. Additionally, one or more off-midline skin incisions may be made to allow for a more direct approach.
Implanting a spinal rod fixation system generally involves at least two steps: (i) placing implants (e.g., screws) into the spine and (ii) inserting a rod between the implants. Proper placement of the implants requires correctly positioning the implants in the spine. The starting insertion point, the trajectory of the implants and the implants' size are crucial to implant placement.
The spinal implant generally comprises a screw portion and a body portion. The screw portion is inserted into the spine. And, the body portion generally has a channel into which a spinal rod is inserted and secured. The rod insertion procedure requires insertion of the rod through an incision in the skin, which may be separate and distinct from the incision through which the implant(s) is placed. In other embodiments, the rod is inserted through the same incision as the implant(s). The rod connects the implants together.
There exists a need for a less invasive spinal implant and rod introduction system that improves direct visualization, enables a rod to be connected to an implant anchored at varying depths in the body and is generally simple to use.